The purpose of the proposed research is to increase our understanding of how the motor cortex controls movement and subsequently to contribute toward the better treatment of human motor dysfunctions. During the past years, we have shown that there is a finer localization of cortical motor function (cortical efferent zone) than has been reported and that there is a loop circuit which connects the efferent zone and the target muscle. During the coming years, we will further characterize the nature of this loop, i.e., the cortical reflex, and investigate the factors which influence the activity of this loop circuit. This will be done by examining the nature of unitary activities recorded from various relay nuclei within the loop crcuit and also by examining the modification of these activities by microstimulation at various parts of the central nervous system. The results will hopefully yield a new method which will detect cortical motor dysfunctions.